A frequent goal in designing wireless communications systems is to increase the number of users that may be simultaneously served by the communications system. This is generally referred to as increasing system capacity. In multiple access communications systems, including code division multiple access (CDMA) wireless communications systems, the use of an adaptive antenna array at the base transceiver has been proposed for increasing system capacity.
An adaptive antenna array includes two or more radiating elements with dimensions, spacing, orientation, and illumination sequences that produce a field pattern on a per-user basis from a combination of fields emitted from individual elements that has greater field intensities in some directions and lesser field intensities in other directions. A base transceiver that adjusts field patterns of an adaptive antenna array on a per-user basis typically uses per-user pilots to fulfill the requirement that the pilot and traffic channel must be substantially in-phase for proper demodulation of the traffic channel. However, utilization of per-user pilots increases complexity and diminishes capacity of the communication system.
For example, per-user pilots dictate longer pilot sequences to accommodate a greater number of pilots, and there is a corresponding increase in complexity of the pilot searcher due to the longer pilot sequences, including increases in computational requirements. In addition, soft handoff complexity is increased with the use of per-user pilots and capacity is reduced with the assignment of an additional per-user pilot during a soft handoff. Furthermore, additional pilots increase power requirements for each traffic channel, thereby reducing the amount of gain obtained with an adaptive antenna array.
In view of the foregoing, is should be appreciated that it would be desirable to provide methods and apparatus for transmitting a traffic channel with an adaptive antenna array without per-user pilots. Furthermore, additional desirable features will become apparent to one skilled in the art from the following detailed description of a preferred exemplary embodiment and appended claims.